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- Fix CVE-2026-42944, Heap overflow and crash with multiple nsid,

Browse Source 
cookie, padding EDNS options. Thanks to Qifan Zhang, Palo Alto
  Networks, for the report.
This commit is contained in:
W.C.A. Wijngaards
2026-05-20 10:13:55 +02:00
parent 6a31e470f8
commit fe946ba4e9
5 changed files with 37 additions and 20 deletions
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doc/Changelog
+3
View File
@@ -1,6 +1,9 @@
20 May 2026: Wouter
- Fix CVE-2026-33278, Possible remote code execution during DNSSEC
validation. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
- Fix CVE-2026-42944, Heap overflow and crash with multiple nsid,
cookie, padding EDNS options. Thanks to Qifan Zhang, Palo Alto
Networks, for the report.
23 April 2026: Wouter
- Merge #1441: Fix buffer overrun in
testcode/unitmain.c
+2 -2
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@@ -1092,7 +1092,7 @@ static void edns_ede_encode_notxt_fit_test( struct query_info* qinfo,
{
struct edns_data edns;
sldns_buffer* pkt;
uint16_t edns_field_size, ede_txt_size;
size_t edns_field_size, ede_txt_size;
int found_ede = 0, found_ede_other = 0, found_ede_txt = 0;
int found_other_edns = 0;
edns_ede_encode_setup(&edns, region);
@@ -1123,7 +1123,7 @@ static void edns_ede_encode_no_fit_test( struct query_info* qinfo,
{
struct edns_data edns;
sldns_buffer* pkt;
uint16_t edns_field_size, ede_size, ede_txt_size;
size_t edns_field_size, ede_size, ede_txt_size;
int found_ede = 0, found_ede_other = 0, found_ede_txt = 0;
int found_other_edns = 0;
edns_ede_encode_setup(&edns, region);
util/data/msgencode.c
+23 -13
View File
@@ -820,7 +820,7 @@ reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
return 1;
}
uint16_t
size_t
calc_edns_field_size(struct edns_data* edns)
{
size_t rdatalen = 0;
@@ -856,7 +856,7 @@ calc_edns_option_size(struct edns_data* edns, uint16_t code)
}
uint16_t
calc_ede_option_size(struct edns_data* edns, uint16_t* txt_size)
calc_ede_option_size(struct edns_data* edns, size_t* txt_size)
{
size_t rdatalen = 0;
struct edns_option* opt;
@@ -958,6 +958,10 @@ attach_edns_record_max_msg_sz(sldns_buffer* pkt, struct edns_data* edns,
padding_option = opt;
continue;
}
if(sldns_buffer_position(pkt) + opt->opt_len + 4 > max_msg_sz)
break; /* no space for it */
if(!sldns_buffer_available(pkt, 4 + opt->opt_len))
break;
sldns_buffer_write_u16(pkt, opt->opt_code);
sldns_buffer_write_u16(pkt, opt->opt_len);
if(opt->opt_len != 0)
@@ -968,12 +972,18 @@ attach_edns_record_max_msg_sz(sldns_buffer* pkt, struct edns_data* edns,
padding_option = opt;
continue;
}
if(sldns_buffer_position(pkt) + opt->opt_len + 4 > max_msg_sz)
break; /* no space for it */
if(!sldns_buffer_available(pkt, 4 + opt->opt_len))
break;
sldns_buffer_write_u16(pkt, opt->opt_code);
sldns_buffer_write_u16(pkt, opt->opt_len);
if(opt->opt_len != 0)
sldns_buffer_write(pkt, opt->opt_data, opt->opt_len);
}
if (padding_option && edns->padding_block_size ) {
if (padding_option && edns->padding_block_size &&
sldns_buffer_position(pkt)+4 <= max_msg_sz &&
sldns_buffer_available(pkt, 4) /* if there is space for it */) {
size_t pad_pos = sldns_buffer_position(pkt);
size_t msg_sz = ((pad_pos + 3) / edns->padding_block_size + 1)
* edns->padding_block_size;
@@ -1017,7 +1027,7 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
{
uint16_t flags;
unsigned int attach_edns = 0;
uint16_t edns_field_size, ede_size, ede_txt_size;
size_t edns_field_size, ede_size, ede_txt_size;
if(!cached || rep->authoritative) {
/* original flags, copy RD and CD bits from query. */
@@ -1044,12 +1054,12 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
* calculate sizes once here */
edns_field_size = calc_edns_field_size(edns);
ede_size = calc_ede_option_size(edns, &ede_txt_size);
if(sldns_buffer_capacity(pkt) < udpsize)
if(sldns_buffer_capacity(pkt) < (size_t)udpsize)
udpsize = sldns_buffer_capacity(pkt);
if(!edns || !edns->edns_present) {
attach_edns = 0;
/* EDEs are optional, try to fit anything else before them */
} else if(udpsize < LDNS_HEADER_SIZE + edns_field_size - ede_size) {
} else if((size_t)udpsize < (size_t)LDNS_HEADER_SIZE + edns_field_size - ede_size) {
/* packet too small to contain edns, omit it. */
attach_edns = 0;
} else {
@@ -1063,13 +1073,13 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
return 0;
}
if(attach_edns) {
if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size)
if((size_t)udpsize >= sldns_buffer_limit(pkt) + edns_field_size)
attach_edns_record_max_msg_sz(pkt, edns, udpsize);
else if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_txt_size) {
else if((size_t)udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_txt_size) {
ede_trim_text(&edns->opt_list_inplace_cb_out);
ede_trim_text(&edns->opt_list_out);
attach_edns_record_max_msg_sz(pkt, edns, udpsize);
} else if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_size) {
} else if((size_t)udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_size) {
edns_opt_list_remove(&edns->opt_list_inplace_cb_out, LDNS_EDNS_EDE);
edns_opt_list_remove(&edns->opt_list_out, LDNS_EDNS_EDE);
attach_edns_record_max_msg_sz(pkt, edns, udpsize);
@@ -1132,7 +1142,7 @@ extended_error_encode(sldns_buffer* buf, uint16_t rcode,
}
sldns_buffer_flip(buf);
if(edns && edns->edns_present) {
uint16_t edns_field_size, ede_size, ede_txt_size;
size_t edns_field_size, ede_size, ede_txt_size;
struct edns_data es = *edns;
es.edns_version = EDNS_ADVERTISED_VERSION;
es.udp_size = EDNS_ADVERTISED_SIZE;
@@ -1144,13 +1154,13 @@ extended_error_encode(sldns_buffer* buf, uint16_t rcode,
* to see if EDNS can fit. */
edns_field_size = calc_edns_field_size(&es);
ede_size = calc_ede_option_size(&es, &ede_txt_size);
if(edns->udp_size >= sldns_buffer_limit(buf) + edns_field_size)
if((size_t)edns->udp_size >= sldns_buffer_limit(buf) + edns_field_size)
attach_edns_record_max_msg_sz(buf, &es, edns->udp_size);
else if(edns->udp_size >= sldns_buffer_limit(buf) + edns_field_size - ede_txt_size) {
else if((size_t)edns->udp_size >= sldns_buffer_limit(buf) + edns_field_size - ede_txt_size) {
ede_trim_text(&es.opt_list_inplace_cb_out);
ede_trim_text(&es.opt_list_out);
attach_edns_record_max_msg_sz(buf, &es, edns->udp_size);
} else if(edns->udp_size >= sldns_buffer_limit(buf) + edns_field_size - ede_size) {
} else if((size_t)edns->udp_size >= sldns_buffer_limit(buf) + edns_field_size - ede_size) {
edns_opt_list_remove(&es.opt_list_inplace_cb_out, LDNS_EDNS_EDE);
edns_opt_list_remove(&es.opt_list_out, LDNS_EDNS_EDE);
attach_edns_record_max_msg_sz(buf, &es, edns->udp_size);
util/data/msgencode.h
+2 -2
View File
@@ -106,7 +106,7 @@ void qinfo_query_encode(struct sldns_buffer* pkt, struct query_info* qinfo);
* @param edns: edns data or NULL.
* @return octets to reserve for EDNS.
*/
uint16_t calc_edns_field_size(struct edns_data* edns);
size_t calc_edns_field_size(struct edns_data* edns);
/**
* Calculate the size of a specific EDNS option in packet.
@@ -127,7 +127,7 @@ uint16_t calc_edns_option_size(struct edns_data* edns, uint16_t code);
* extra text.
* @return octets the option will take up.
*/
uint16_t calc_ede_option_size(struct edns_data* edns, uint16_t* txt_size);
uint16_t calc_ede_option_size(struct edns_data* edns, size_t* txt_size);
/**
* Attach EDNS record to buffer. Buffer has complete packet. There must
util/data/msgparse.c
+7 -3
View File
@@ -950,6 +950,7 @@ parse_edns_options_from_query(uint8_t* rdata_ptr, size_t rdata_len,
struct comm_reply* repinfo, uint32_t now, struct regional* region,
struct cookie_secrets* cookie_secrets)
{
int nsid_seen = 0, cookie_seen = 0, padding_seen = 0;
/* To respond with a Keepalive option, the client connection must have
* received one message with a TCP Keepalive EDNS option, and that
* option must have 0 length data. Subsequent messages sent on that
@@ -984,8 +985,9 @@ parse_edns_options_from_query(uint8_t* rdata_ptr, size_t rdata_len,
/* handle parse time edns options here */
switch(opt_code) {
case LDNS_EDNS_NSID:
if (!cfg || !cfg->nsid)
if (!cfg || !cfg->nsid || nsid_seen)
break;
nsid_seen = 1;
if(!edns_opt_list_append(&edns->opt_list_out,
LDNS_EDNS_NSID, cfg->nsid_len,
cfg->nsid, region)) {
@@ -1027,8 +1029,9 @@ parse_edns_options_from_query(uint8_t* rdata_ptr, size_t rdata_len,
case LDNS_EDNS_PADDING:
if(!cfg || !cfg->pad_responses ||
!c || c->type != comm_tcp ||!c->ssl)
!c || c->type != comm_tcp ||!c->ssl || padding_seen)
break;
padding_seen = 1;
if(!edns_opt_list_append(&edns->opt_list_out,
LDNS_EDNS_PADDING,
0, NULL, region)) {
@@ -1039,8 +1042,9 @@ parse_edns_options_from_query(uint8_t* rdata_ptr, size_t rdata_len,
break;
case LDNS_EDNS_COOKIE:
if(!cfg || !cfg->do_answer_cookie || !repinfo)
if(!cfg || !cfg->do_answer_cookie || !repinfo || cookie_seen)
break;
cookie_seen = 1;
if(opt_len != 8 && (opt_len < 16 || opt_len > 40)) {
verbose(VERB_ALGO, "worker request: "
"badly formatted cookie");